Prince of Wales Hospital Neuro-Radiology SPINE Raj Reddy Neurosurgery Prince of Wales Hospital

Objectives Review spine anatomy on X-ray, CT and MRI Approach to interpretation of imaging Differential diagnoses for common spine lesions

Imaging Modalities

Basic Imaging Types X-ray CT (Computed Tomography) MRI (Magnetic Resonance Imaging) Angiography

X-ray Limited Use Evaluation of: Bones (fractures) Calcification

Computed Tomography http://fitsweb.uchc.edu/student/selectives/TimHerbst/intro.htm

Computed Tomography (CT) Imaging in sections, or slices Computed Geometric processing used to reconstruct an image Computerized algorithms

Computed Tomography Uses X-rays Dense tissue, like bone, blocks x-rays Gray matter weakens (attenuates) the x-rays Fluid attenuates even less A computerized algorithm (filtered backprojection) reconstructs an image of each slice

CT Image Formation X-ray tube X-ray X-ray detector

CT Image Formation Backprojection

CT Image Reconstruction – 6 Slices

CT Image Reconstruction – 12 Slices

CT Image Reconstruction – Final

Magnetic Resonance Imaging

What is MR? Not an X-ray, electromagnetic Electromagnetic field aligns all the protons in the brain Radiofrequency pulses cause the protons to spin Amount of energy emitted from the spin is proportional to number of protons in the tissue No ferromagnetic objects

Angiography

Angiography Real time X-ray study Catheter placed through femoral artery is directed up aorta into the cerebral vessels Radio-opaque dye is injected and vessels are visualized Gold standard for studying cerebral vessels.

Angiography AP Right ICA Lateral Right ICA

Angiography AP Right Vertebral

Planes of Section Axial (transverse) Sagittal Coronal Oblique

Anatomy

Radiographic Anatomy

Cervical Spine – AP View

Cervical Spine – Lateral View

Cervical Spine – Open-Mouth (Dens) View

Cervical Spine – Oblique View

Lumbar Spine – AP View

Lumbar Spine – Lateral View

Approach to Xrays

Approach to Spine Imaging A – adequacy/alignment B – bone C – cord/canal/cartilage D – disc E – extras

C7-T1

Alignment 1. prevertebral 2. anterior spinal 3. posterior spinal 4. spino-laminar

Cartilage Predental Space should be no more than 3 mm in adults and 5 mm in children Increased distance may indicate fracture of odontoid or transverse ligament injury

Cartilage Disc Spaces Assess spaces between the spinous processes Should be uniform Assess spaces between the spinous processes

Soft tissue Nasopharyngeal space (C1) - 10 mm (adult) Retropharyngeal space (C2-C4) - 5-7 mm Retrotracheal space (C5-C7) - 14 mm (children), 22 mm (adults) Extremely variable and nonspecific

CT Anatomy

CT

MRI Anatomy

Compartments of the Spine a. Intradural, intramedullary b. Intradural, extramedullary c. Extradural, extramedullary a. b. c.

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Pathology

Spine Pathology Trauma Degenerative disease Tumors and other masses Inflammation and infection Vascular disorders Congenital anomalies

Trauma

Evaluating Trauma Fracture – plain film / CT Dislocation – plain film / CT Ligamentous injury – MRI Cord injury – MRI Nerve root avulsion – MRI

To x-ray or not to x-ray? 13 million trauma patients at risk for cervical spine injury very low incidence of cervical spine fracture In alert and stable trauma patients: x-rays performed on 69% CT performed in 5% acute injury in 2.6% stabilization in 2.2% Stiell IG et al. The Canadian C-Spine Rule versus NEXUS in Patients with Trauma. N Engl J Med. 2003.

NEXUS C-Spine Rules

Canadian C-Spine Rules (CCR) Stiell IG. The CCR in Alert and Stable Trauma Patients. JAMA. 2001.

Which one is better? NEXUS Pro: easy to use Con: poor sensitivity and specificity (90.7% and 36.8%) Con: more x-rays (67%) CCR Pro: great sensitivity and specificity (99.4% and 45.1%) Pro: less x-rays (55.9%) Con: more difficult to remember and use Stiell IG et al. The Canadian C-Spine Rule versus NEXUS in Patients with Trauma. N Engl J Med. 2003.

Plain film findings may be very subtle or absent! Anterolisthesis of C6 on C7 (Why?)

Fractures of C6 left pedicle and lamina

CT – 2D Reconstructions Acquire images axially… …reconstruct sagittal / coronal

26M MVA

Vertebral body burst fx with retropulsion into spinal canal 2D Reformats

Vertebral Artery Dissection/Occlusion Secondary to C6 Fracture

Hyperflexion fx with ligamentous disruption and cord contusion

Nerve root avulsion Axial Coronal Sagittal

Degenerative Disease

Degenerative Disc (and Facet Joint) Disease Foraminal stenosis Thickening/Buckling of Ligamentum Flavum

Degenerative Disc (and Facet Joint) Disease

Degenerative Disc (and Facet Joint) Disease

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis MR# 1471054

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis Disc bulge, facet hypertrophy and flaval ligament thickening frequently combine to cause central spinal stenosis Note the trefoil shape of stenotic spinal canal

Lumbar Spinal Stenosis Disc bulge, facet hypertrophy and flaval ligament thickening frequently combine to cause central spinal stenosis Note the trefoil shape of stenotic spinal canal

Foraminal Stenosis Neural foramen

Cervical Spinal Stenosis

MRI - Degenerative Disc Disease Age: 20-40 36% have degenerated disc 50 85-95% have degenerated disc 60-80 98% have degenerated disc <60 20% have asymptomatic disc herniation Conclusion: Abnormal findings on MRI frequently DO NOT relate to symptoms (and vice versa) !

MRI – Herniated Disc Levels 85-95% at L4-L5, L5-S1 5-8% at L3-L4 2% at L2-L3 1% at L1-L2, T12-L1 Cervical: most common C4-C7 Thoracic: 15% in asymptomatic pts. at multiple levels, not often symptomatic

Schematic sagittal anatomical sections showing the differentiating features of an annular tear (radial tear in this case) and a disc herniation. The term "tear" is used to refer to a localized radial, concentric, or horizontal disruption of the anulus without associated displacement of disc material beyond the limits of the intervertebral disc space. Nuclear material is shown in black, and the annulus (internal and external) corresponds to the white portion of the intervertebral space. The same convention is used in Figures 3, 12, 13, and 14. (Adapted from Milette PC. The proper terminology for reporting lumbar intervertebral disk disorders. AJNR Am J Neurorad 1997;18:1859-66; with permission.) Annular

Symmetrical presence (or apparent presence) of disc tissue "circumferentially" (50-100%) beyond the edges of the ring apophyses may be described as a "bulging disc" or "bulging appearance", and is not considered a form of herniation. Furthermore, “bulging” is a descriptive term for the shape of the disc contour and not a diagnostic category. Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Asymmetrical bulging of the disc margin (50%-100%), such as is found in severe scoliosis, is also not considered a form of herniation. Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

By convention, a "broad-based" herniation involves between 25% and 50% (90-180) of the disc circumference. Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

By convention, a "focal herniation" involves less than 25% (90) of the disc circumference. Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material (see definitions in text). Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Protrusion Extrusion Extrusion When a relatively large amount of disc material is displaced, distinction between protrusion (A) and extrusion (B or C) will generally only be possible on sagittal MR sections or sagittal CT reconstructions. In Figure C, although the shape of the displaced material is similar to that of a protrusion, the greatest cranio-caudal diameter of the fragment is greater than the cranio-caudal diameter of its base at the level of the parent disc, and the lesion therefore qualifies as an extrusion. In any situation, the distance between the edges of the base, which serves as reference for the definition of protrusion and extrusion, may differ from the distance between the edges of the aperture in the anulus, which cannot be assessed on CT images and is seldom appreciated on MR images. In the cranio-caudal direction, the length of the base cannot exceed, by definition, the height of the intervertebral space (Adapted from Milette PC. Classification, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:1267-1292) Protrusion Extrusion Extrusion Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Protrusion w/ migration + sequestration Protrusion w/ migration Schematic representation of various types of posterior central herniations. A, Small sub-ligamentous herniation (or protrusion) without significant disc material migration. B, Sub-ligamentous herniation with downward migration of disc material under the posterior longitudinal ligament (PLL). C, Sub-ligamentous herniation with downward migration of disc material and sequestered fragment (arrow). (From Milette PC. Classification, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:1267-1292) Protrusion w/ migration + sequestration Protrusion w/ migration Protrusion Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Abnormal Disc Herniation Bulge Broad-based Focal Symmetric Asymmetric < 180º > 180º Herniation Bulge 90º–180º < 90º Broad-based Focal Symmetric Asymmetric Waist* No waist Extrusion Protrusion Sequestered Migrated Neither *(In any plane) Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Central Disc Protrusion

L5-S1 Disc Extrusion Into Lateral Recess with Impingement of R S1 Nerve Root MR#1009322

Schmorl’s Nodes

Cervical Radiculopathy

Lumbosacral Radiculopathy (Sciatica) Important: A herniated disc at (e.g.) L4-5 may impinge either the L4 or L5 nerve roots!

L5-S1 Disc Extrusion Into Lateral Recess with Impingement of R S1 Nerve Root MR#1009322

Spondylolysis / Spondylolisthesis

Confusing “Spondy-” Terminology Spondylosis = “spondylosis deformans” = degenerative spine Spondylitis = inflamed spine (e.g. ankylosing, pyogenic, etc.) Spondylolysis = chronic fracture of pars interarticularis with nonunion (“pars defect”) Spondylolisthesis = anterior slippage of vertebra typically resulting from bilateral pars defects Pseudospondylolisthesis = “degenerative spondylolisthesis” (spondylolisthesis resulting from degenerative disease rather than pars defects)

Tumors and Other Masses

Classification of Spinal Lesions Extradural = outside the thecal sac (including vertebral bone lesions) Intradural / extramedullary = within thecal sac but outside cord Intramedullary = within cord

Common Extradural Lesions Herniated disc Vertebral hemangioma Vertebral metastasis Epidural abscess or hematoma Synovial cyst Nerve sheath tumor (also intradural/extramedullary) Neurofibroma Schwannoma

Common Intradural Extramedullary Lesions Nerve sheath tumor (also extradural) Neurofibroma Schwannoma Meningioma Drop Metastasis

Common Intramedullary Lesions Astrocytoma Ependymoma Hemangioblastoma Cavernoma Syrinx Demyelinating lesion (MS) Myelitis

Classification of Spinal Lesions Dura Cord Intradural Extramedullary Extradural Intramedullary

Extradural: Vertebral Body Tumor

Extradural: Vertebral Metastases MR# 1890170 T2 (Fat Suppressed) T1 T1+C (fat suppressed)

Extradural: Vertebral Metastases ? T2 (Fat Suppressed) T1 T1+C (fat suppressed)

Vertebral Metastases vs. Hemangiomas Hemangiomas (Benign, usually asymptomatic, commonly incidental): Bright on T1 and T2 (but dark with fat suppression) Enhancement variable Metastases: Dark on T1, Bright on T2 (even with fat suppression) Enhancement

Vertebral Hemangiomas

Extradural: Vertebral Metastases Diffusely T1-hypointense marrow signal may represent widespread vertebral metastases as in this patient with prostate Ca This can also be seen in the setting of anemia, myeloproliferative disease, and various other chronic disease states

Extradural: Epidural Abscess

Extradural: Nerve Sheath Tumor (Schwannoma)

Intradural Extramedullary: Meningioma

Intradural Extramedullary: Meningioma

Intradural Extramedullary: Nerve Sheath Tumor (Neurofibroma)

Intradural Extramedullary: “Drop Mets” MR#1714289 T2 T1 T1+C

Intradural Extramedullary: “Drop Mets”

Intradural Extramedullary: Arachnoid Cyst T2 T1

Intramedullary: Astrocytoma

Intramedullary: Astrocytoma

Intramedullary: Cavernoma

Intramedullary: Ependymoma

Intramedullary: Syringohydromyelia Seen with: congenital lesions Chiari I & II tethered cord acquired lesions trauma tumors arachnoiditis idiopathic

Intramedullary: Syringohydromyelia Seen with: congenital lesions Chiari I & II tethered cord acquired lesions trauma tumors arachnoiditis idiopathic

Confusing “Syrinx” Terminology Hydromyelia: Fluid accumulation/dilatation within central canal, therefore lined by ependyma Syringomyelia: Cavitary lesion within cord parenchyma, of any cause (there are many). Located adjacent to central canal, therefore not lined by ependyma Syringohydromyelia: Term used for either of the above, since the two may overlap and cannot be discriminated on imaging Hydrosyringomyelia: Same as syringohydromyelia Syrinx: Common term for the cavity in all of the above

Infection and Inflammation

Infectious Spondylitis / Diskitis Common chain of events (bacterial spondylitis): Hematogenous seeding of subchondral VB Spread to disc and adjacent VB Spread into epidural space  epidural abscess Spread into paraspinal tissues  psoas abscess May lead to cord abscess

Infectious Spondylitis / Diskitis T2 T1 T1+C T1+C

Infectious Spondylitis / Diskitis

Pyogenic Spondylitis / Diskitis with Epidural Abscess

T1 T2

Spinal TB (Pott’s Disease) Prominent bone destruction More indolent onset than pyogenic Gibbus deformity Involvement of several VB’s T1 + C

Spinal TB (Pott’s Disease) Prominent bone destruction More indolent onset than pyogenic Gibbus deformity Involvement of several VB’s

Transverse Myelitis Inflamed cord of uncertain cause Viral infections Immune reactions Idiopathic Myelopathy progressing over hours to weeks DDX: MS, glioma, infarction

Multiple Sclerosis Inflammatory demyelination eventually leading to gliosis and axonal loss T2-hyperintense lesion(s) in cord parenchyma Typically no cord expansion (vs. tumor); chronic lesion may show atrophy

Multiple Sclerosis Inflammatory demyelination eventually leading to gliosis and axonal loss T2-hyperintense lesion(s) in cord parenchyma Typically no cord expansion (vs. tumor); chronic lesion may show atrophy

venous hypertension (e.g. AV fistula) Cord Edema As in the brain, may be secondary to ischemia (e.g. embolus to spinal artery) or venous hypertension (e.g. AV fistula) Dural AVF MR#1316826

Vascular

Spinal AVM / AVF

Congenital

MR#1868533 Lipomyelomeningocele with tethered cord, mistaken for myelomenigocele at birth and partially resected without untethering cord. Now 11 y/o with progressive cavovarus deformity, LE weakness and incontinence.

Spine Imaging Guidelines Uncomplicated LBP usually self-limited, requires no imaging Consider imaging if: Trauma Cancer Immunocompromise / suspected infection Elderly / osteoporosis Significant neurologic signs / symptoms Back pain with signs / symptoms of spinal stenosis or radiculopathy, no trauma: Start with MRI; use CT if: Question regarding bones or surgical (fusion) hardware Resolve questions / solve problems on MRI (typically use CT myelography) MRI contraindicated

Spine Imaging Guidelines Begin with plain films for trauma; CT to solve problems or to detail known fractures; MRI to evaluate soft-tissue injury (ligament disruption, cord contusion) MRI for sx of radiculopathy, cauda equina syn, cord compression, myelopathy Fusion hardware is safe for MRI but may degrade image quality; still worth a try Indications for IV contrast in MRI: Tumor, infection, inflammation (myelitis), any cord lesion Post-op L-spine (discriminate residual/recurrent disk herniation from scar) Emergent or scheduled? Emergent only if immediate surgical or radiation therapy decision needed (e.g. cord compression, cauda equina syndrome) Difficult to image entire spine in detail; target study to likely level of pathology CT chest/abdomen/pelvis includes T-L spine (no need to rescan trauma pts*) * If image data still on scanner (24-48 hours)